Apparatus for recapping a tire with a flexible segmented mold

ABSTRACT

A method and apparatus for retreading a tire includes a mold segment (14) having open ends (16) and (18). A tire carcass (10) has a layer of uncured rubber (12) built up on the surface thereof. The mold (14) is disposed therearound with ribs (20) resting on the surface thereof. A semi-flexible cap (24) is disposed over the ends (16) and (18) which are separated by a gap (20). An elastic strap (26) is then wrapped about the assembly to secure the mold (14) to the built up tire carcass (10). An envelope (28) is then wrapped about the assembled tire carcass (10) to provide a radially inward force thereto. The whole assembly is then cured in a curing oven.

RELATED APPLICATIONS

This application is a division of application Ser. No. 601,543, filedApr. 18, 1984, now U.S. Pat. No. 4,588,460 issued May 13, 1986.

TECHNICAL FIELD OF THE INVENTION

The present invention pertains in general to tire recapping and, moreparticularly, to tire recapping with flexible segmented molds.

BACKGROUND OF THE INVENTION

The recapping of tires with flexible molds has heretofore beenaccomplished by first building up a layer of uncured rubber on a buffedtire carcass. A flexible ring mold having a negative tread patternimprint is then placed around the built-up tire and the whole assemblyplaced in a sealing envelope. This whole assembly is then placed into avulcanizing chamber and the rubber is cured with the imprint of the moldcontained therein.

During placement of the mold over the built-up tire, the mold must bestretched and expanded to allow the tread pattern to fit around thebuild up tire. Alternatively, the tire must be "buckled" to receive themold and then inflated against the mold. During curing of the rubberwith the mold so disposed, the rubber assumes a plastic state, therebyallowing the mold tread pattern to sink into the rubber to form thepositive contour of the tread. This process is normally assisted by someform of external force such as high chamber pressure applied to themold, the aspiration and resiliency of the sealing envelope or pressureapplied to the build up tire to force outward against the mold.

A prior retread method utilizing a flexible continuous mold is disclosedin U.S. Pat. No. 4,053,265 issued to Wulker on Oct. 11, 1977. The Wulkerpatent discloses an expandable continuous or ring mold that is resilientenough to resume its initial state after it is stretched and disposedabout the tire. However, several disadvantages exist in this type ofmold in that the mold is difficult to stretch for disposal about thetire. This process is relatively difficult and usually requiresexpensive equipment and often more than one operator to place the moldabout the tire. If the mold is not properly placed about the tire,misalignment of tread design can occur which would result in a reject.Moreover, repeated stretching of such prior molds can causedeterioration of the molds.

Ring molds of this type also have the disadvantage that a separate ringmold must be provided for each tire size and each ring mold mustaccommodate all variances in a given tire size. Depending upon the tiresize, the circumference between various tires within a particular sizecan vary as much as one to fiVe inches. As the tire size varies, theclearance between the mold and the build-up tire also varies. Thisvariance results in additional problems in placing the mold on thebuilt-up tire and can cause misalignment of the tread pattern during thehandling and vulcanization process.

In view of the above, there exists a need for a tire retreading processthat utilizes a mold that is relatively easy for an operator to utilizeand which accommodates the variations in a given tire size.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and theadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying Drawings in which:

FIG. 1 illustrates a perspective view of a flexible mold in accordancewith the present invention being placed around a prepared tire carcass;

FIG. 2 illustrates a stitcher imbedding the mold into the uncured rubberlayer on the prepared tire carcass;

FIG. 3 illustrates a cutaway perspective view of a built up tire withthe mold in place and illustrating the gap between two sections of themold;

FIG. 4 illustrates a cross-sectional view of the mold of FIG. 3;

FIG. 5 illustrates a schematic diagram of a tire utilizing a singlesegment mold having a single gap;

FIG. 6 illustrates a schematic diagram of a tire with two section molddisposed therearound;

FIG. 7 illustrates a schematic diagram of a tire having a four sectionmold disposed thereabout;

FIG. 8 illustrates a schematic diagram of a tire with the two sectionmold disposed thereabout and sealing caps adjacent the gaps;

FIG. 9 illustrates an alternate embodiment of the view of FIG. 8 with asegment disposed in the gap to accommodate varying tire sizes;

FIG. 10 illustrates an alternate embodiment of the mold of FIG. 8 withnylon tape spread across the gaps to facilitate placement;

FIG. 11 illustrates the mold of FIG. 10 with the mold opened up;

FIG. 12 illustrates a planar view of the gap in FIG. 10;

FIG. 13 illustrates a planar view of an alternate embodiment of the gapsecuring device with a series of snaps utilized;

FIG. 14 illustrates a restraining device utilized to limit the size ofthe gap;

FIG. 15 illustrates a planar view of a spacing member utilized to presetthe gap;

FIG. 16 illustrates a side view of the spacing member of FIG. 15; and

FIG. 17 illustrates an interlocking mechanism to prevent relativelateral movement of the mold segments.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, there is illustrated a perspective view of asegmented mold 14 for use in recapping a tire in accordance with thepresent invention. The mold 14 is a one piece flexible mold that is notcontinuous about the circumference thereof and is split at one point toform two defined ends 16 and 18. A series of ribs 20 are formed on theinner surface of the mold 14 and comprise the negative contour of thedesired tread pattern that is to be imprinted in the recapped tire.

Referring now to FIG. 2, there is illustrated a prepared tire carcass 10which is prepared by buffing the surface thereof and applying cementthereto. A layer of uncured rubber 12 is then built up on the surface ofthe tire carcass 10 to provide a built-up tire. In accordance with thepresent invention, the ends 16 and 18 are separated and the built-uptire carcass 10 disposed therein. It is very important to place the ribs20 of the tread pattern against the uncured rubber layer 12 with aminimum amount of movement therebetween. If the ribs 20 were allowed tomove relative to the uncured rubber layer 12 during placement of themold 14 about the built-up tire carcass 10, misalignment of the treadpattern could occur. To prevent this, the mold 14 and the built-up tirecarcass 10 are placed onto an arcuate roller bed 11 that conforms to thesurface of the mold 14. This roller bed 11 is referred to as a"stitcher". A hold down roller arm 13 is then lowered against thebuilt-up tire carcass 10 and mold 14 external to the mold 14 anddiametrically opposite the roller bed 11. The hold down roller 13presses the ribs 20 into the uncured rubber layer 12 to minimize lateralmovement of the mold 14 relative to the built-up carcass 10. Both themold 14 and built-up tire carcass 10 are then rotated together until themold 14 fully encircles the built-up tire carcass 10. As will bedescribed hereinbelow, a gap is formed between the ends 16 and 18 of apredetermined maximum dimension and this may require passing theassembled unit through the apparatus of FIG. 2 until the desireddimension of this gap is realized. By utilizing the flexible mold 14 asa segmented mold rather than a continuous ring type mold, the need forstretching the mold about the built-up tire carcass 10 is eliminited.This results in less stretch on the mold.

Referring now to FIGS. 3 and 4, there are shown perspective andcross-sectional views, respectively, of the flexible recapping mold 14mounted on the tire carcass 10. When the mold 14 is initially placedabout the built-up tire, the outer ends of the ribs 20 touch theexterior surface of the uncured rubber layer 12 leaving space betweenthe innermost areas of the mold 14 and the built-up tire. This resultsin an expansion of the circumference of the mold 14 about the built-uptire carcass 10. Since the mold is segmented and not a continuous ring,a gap 22 is formed between the free ends 16 and 18. Gap 22 may vary independence with the tire circumference, as the mold 14 may accommodatevarious tire sizes. When the ribs 20 are pressed into the layer ofuncured rubber 12 during curing, as will be subsequently described, theoverall circumference of the mold 14 decreases and the ends 16 and 18tend to abut. If the gap 22 were not provided, the overall circumferenceof the mold 14 could not decrease without the ends 16 and 18 pressingagainst each other and causing a deformation in the mold 14.

After the mold 14 is disposed around the built-up tire, a semi-flexiblecap 24 is then disposed over the gap 22. The semi-flexible cap 24extends several inches on each side of the mold gap 22 and is operableto prevent the ends 16 and 18 of the mold 14 from abutting and pushingradically outward, thereby distorting the tread pattern. Thesemi-flexible cap 24 can be fabricated from a synthetic rubber compound,which provides a semi-flexible conformation. This synthetic rubbercompound can be a blend of styrene butadiene and natural rubber.

A strip 26 is disposed around the assembly of the mold 14 and built uptire carcass 10. The strip 26 is functional to secure the mold 14 andthe cap 24 firmly against the layer of uncured rubber 12 to facilitatehandling. The strip 26 can range between two inches to six inches inwidth and may compromise either a continuous elastic band fabricatedfrom Chlorobutyl or preshrunk nylon cured tape. The elastic band needonly be stretched around the assembly, whereas the nylon tape must bestapled at one end, then wrapped about the assembly and then stapled atthe free end to the mold 14. The nylon tape is manufactured by BurkeNarrow Fabric Corp., Charlotte, N.C. In placing the strip 26 about themold, it is first wet and, after placement, heated to promote shrinkage.A typical volumetric shrinkage is from six to eight percent.

After the mold is secured about the built-up tire, the assembly isplaced into a conventional flexible tubular or toroidal rubber envelope28 which is described in U.S. Pat. Nos. 4,053,265, 4,269,644 and4,185,056, each of which is incorporated herein by reference. Theflexible envelope 28 has an air passage 30 connected thereto forcommunicating the interior of the flexible envelope 28 to the exteriorthereof. The flexible envelope 28 is tightly fitted to force the moldagainst the layer of uncured rubber and is functional to evacuate airthat surrounds the mold and the uncured rubber layer 12 during curingthereof. In so doing, gas is prevented from being entrapped between themold and the uncured rubber layer 12. The strip 26 functions as a"wicking" layer to aid in dispelling gas from between the tread andmold.

The assembly with the flexible envelope 28 disposed therearound is thenplaced onto a rim and the tire carcass 10 pressurized. This pressurizedassembly is then placed into an evacuated curing oven and thetemperature raised to approximately 212°-300° F. This is a conventionalcuring process and is further described in U.S. Pat. Nos. 4,185,056 and4,269,644. The pressure in the chamber is less than the pressureinternal to the tire carcass 10 such that a differential in pressureresults. This differential pressure, in addition to the pressure of theenvelope 28 about the tire, forces the ribs 20 into the uncured rubberlayer 12 and brings the ends 16 and 18 into abutment. The layer 12 isthen allowed to cure, thus retaining the imprint of the ribs 20.

When the assembly of FIG. 4 in the flexible envelope 28 is placed intothe curing oven, the ribs 20 of the mold 14 begin to press into thelayer 12 when sufficient heat is supplied thereto prior to anysignificant curing. As the mold 14 sinks into the layer 12, the outercircumference of the mold 14 decreases. This results in a decrease indimension for the gap 22 and abutment of the edges 16 and 18. It isimportant to dimension the mold such that the final position of the mold14 upon curing of the layer 12 allows the ends 16 and 18 tosubstantially abut since the mold 14 has not been deformed bystretching. If an excessive amount of force results from abutment of theends 16 and 18, the ends will tend to push radially outward from thetire. The cap 24 tends to disperse this outward force. A typical gapbetween the ends 16 and 18 may be 1/8 to 3/8 inch for a passengervehicle and 1/4 to 1/2 inch for truck tire.

The mold 14 is initially fabricated by forming a layer of uncured rubberabout a circular reference matrix having the positive contour of thedesired tread pattern. This layer of uncured rubber is then cured byconventional techniques and then peeled away from the matrix. The moldcan then be cut at one or more positions to make corresponding segments.Alternatively, the reference matrix may be in the shape of a segment. Ifthe mold is fabricated from conventional materials, it may be necessaryto employ the use of a mold release layer between the mold 14 and theuncured rubber layer 12 such that removal of the mold 14 after curing isfacilitated. In addition, a wicking layer may also be employedtherebetween to aid in venting gasses. In the preferred embodiment, thematerial utilized is a rubber manufactured under the tradenameChlorobutyl manufactured by Exxon Chemical Americas in Houston, Tex.,although numerous other rubber types may be alternatively used. Aspecific example of the use of Chlorobutyl is as follows:

    ______________________________________                                                             Manufacturer                                                      Manufacturer                                                                              or Commercial  Parts by                                  Material or Source   Designation    Volume                                    ______________________________________                                        elastomer                                                                              Exxon       Chlorobutyl HT-1066                                                                          100.00                                    carbon   Commercially                                                                              N330           60.00                                     black    available                                                            magnesium                                                                              Commercially                                                                              Maglite        .35                                       oxide    available                                                            Napthenic                                                                              Sun Oil     Circosol oil   5.00                                      oil                  (4240)                                                   Stearic  Commercially                                                                              Stearic acid Flake                                                                           1.00                                      acid     available                                                            Dyphene  Sherwin     Dyphene 8318   2.00                                               Williams                                                             Zinc     Commercially                                                                              Zinc Oxide     5.00                                      Oxide    available                                                            Tetra    Commercially                                                                              TMTD           1.00                                      Methyl   available                                                            Thiuran                                                                       DiSulfide                                                                     Mercapto Commercially                                                                              MBTS           1.50                                      Benzyl   available                                                            Thiazole                                                                      DiSulfide                                                                     ______________________________________                                    

Chlorobutyl rubber may be utilized both for the mold 14 and for the cap24. The properties of Chlorobutyl facilitate removal of the mold fromthe layer 12 after curing of the tire without the necessity of a moldrelease layer. In addition, the presence of the gap 22 allows the layer12 to be cured without the requirement for a wicking layer since gassescan escape through the gap 22.

Referring now to FIG. 5, there is illustrated a schematic diagram of themold 14 disposed about the built up tire carcass 10. Dotted linesillustrate the position of the mold 14 prior to insertion into the ovenand the solid lines illustrate the position wherein the gap 22 isclosed. In designing the mold, the amount of "sink" for the tread ribsinto the rubber must be accounted for, as well as the circumference ofthe inner surface of the mold. For example, if the built-up tirecircumference is set equal to the inner surface mold circumference andboth are equal to 80 inches and a typical tread rib has a depth ofapproximately 0.312 inches, this would result in a rib circumference ofapproximately 78 inches. Therefore, the difference between the ribcircumference and the circumference of the inner surface of the moldwould be approximately two inches. This would cause the gap 22 to beapproximately two inches if the ribs 20 did not penetrate into theuncured rubber layer 12. However. in placing the mold about the built-uptire, the apparatus described in FIG. 2 is utilized for initiallyplacing the layer of uncured rubber 12 onto the tire carcass 10. Byusing the stitcher, the ribs 20 can be pressed into the layer 12 suchthat they partially penetrate the surface, thereby forming a smallergap. Preferably, the gap should be between 0.125 inches to 0.475 inches,although the gap lenth may substantially vary depending upon the tiretype. The gap should never exceed optimum limits established for a giventire size.

Referring now to FIG. 6, there is illustrated a schematic diagram for analternate embodiment that utilizes two segmented half molds 32 and 34.The two half molds 32 and 34 are similar to the single mold 14 exceptthat the resulting assembly will have two gaps. In FIG. 7 there isillustrated a schematic diagram utilizing four mold segments 36, 38, 40and 42. By utilizing two or more segments, it is possible to reduce theinitial gap without having to significantly press the mold segments intothe uncured rubber layer 12. For example, the four segment mold of FIG.7 as applied to the above described example would allow a total of twoinches worth of gap. This gap is divided between all four segments,thereby resulting in gaps of a maximum of 0.5 inches. The range of eachspecific gap does not change, but the accumulated gap spread increasesbecause of the increased number of gaps.

Referring now to FIG. 8, there is illustrated a schematic diagram of thetwo segment mold of FIG. 6 prior to curing. Initially, the mold halves32 and 34 have a gap 44 formed at one end and a gap 46 formed at theother end. A cap 48 is disposed adjacent the gap 44 and a cap 50 isdisposed adjacent the gap 46. The caps 48 and 50 are similar to the cap24. Prior to curing, the elastic band 26 (not shown) is wrapped aboutthe assembly to secure the caps 48 and 50 against the mold halves 32 and34 and in general immobilize the mold halves 32 and 34 and the caps 48and 50. The assembly is then placed into an envelope, a rim disposedwithin the tire carcass 10 and pressure applied thereto. This assemblyis then placed into a curing oven according to the process describedabove.

Referring now to FIG. 9, there is illustrated an alternate embodiment ofthe mold of FIG. 8 with the mold halves 32 and 34 disposed about a tirecarcass 10'. The built-up tire carcass 10' has a diameter that isslightly larger than the built-up tire carcass 10. To accommodate forthis increased circumference, a mold sizing segment 52 is disposedbetween the ends of the mold halves 32 and 34, thus forming a gap 54 anda gap 56. Each of the gaps 54 and 56 are dimensioned similar to the gaps44 and 46 of FIG. 6. Segment 52 is a combination of the tread pattern ofmold segments 32 and 34. The elastic band 26 (not shown) is then wrappedabout the mold halves 32 and 34, the sizing segment 52 and the caps 48and 50.

In retreading conventional tires, a given tire size may vary from one tofive inches in circumference, depending upon the tire type, which is asignificant percentage that must be accounted for. By placing the sizingsegment 52 between the ends of the two mold sections 32 and 34, thisvariance can be accommodated, such that the mold ends adjacent all ofthe gaps abut when the tire is cured. Without this segment, various sizemold halves are required. In addition, a series of segments can beprovided such that one set of mold halves can span between two to threetire sizes, thereby reducing the inventory of molds that must becarried. When an operator is placing the mold halves about the built-uptire, it is then only necessary to place the proper segment between theends of mold halves to properly size the tire for both tire size andvariance within that tire size.

Referring now to FIGS. 10 and 11, there is illustrated the preferredembodiment of the view of FIG. 8 utilizing the mold halves 32 and 34,wherein like numerals refer to like parts in the two figures. To aid indimensioning the gaps properly, a layer 58 of nylon tape is disposedacross the gap 44 and a layer 60 of nylon tape is disposed across thegap 46. Each of the layers 58 and 60 are stapled on either sides of therespective gaps to define the maximum gap width. This eliminates therequirement for the first layer of tape 26, as described above withreference to FIG. 3.

In constructing the assembly of FIG. 10, the mold half 32 is firstplaced onto the built-up tire carcass 10 using the stitcher of FIG. 2and then the second mold half 34 has one end thereof placed adjacent themold half 32 to form the gap 46 within the appropriate constraints. Thetape layer 60 is then stapled to prevent the gap 46 from increasingbeyond these constraints. The mold half 32 is then stitched with theapparatus of FIG. 2 to the remaining part of the built-up tire carcass10 until the gap 44 is within the constraints. At this point, the tapelayer 58 is stapled across the gap 44. The caps 48 and 50 are thenplaced over the layers 58 and 60 and the assembly processed as describedabove. When the mold halves 32 and 34 are removed from the cured tire,it is only necessary to unstaple one side of the layer 58 and leave thelayer 60 attached to each of the halves 32 and 34. This results in theassembly of FIG. 12 wherein the tape layer 60 remains in place.

Referring now to FIG. 12, there is illustrated a planar view of the tapelayer or strap 58 which is comprised of two strips disposed across thegap 44 and spaced apart. As described above, the straps 58 are attachedto the mold half 32 by staples 62 and attached to the mold half 34 bystaples 64. When the two mold halves 32 and 34 abut together, the strap58 is resilient enough to buckle, thereby preventing an opposingtangential force at the gap 44. The straps 58 and 60 can be fabricatedof Chlorobutyl.

An alternate embodiment of straps 58 and 60 which does not requirestaples is illustrated in FIG. 13. The strap 58 is attached to the moldhalf 32 by snaps 66 and to the mold half 34 by snaps 68. By utilizingsnaps, the mold halves 32 and 34 can be fabricated in a ready-to-usecondition. By disposing the mating halves of the snaps at theappropriate distances, it is not necessary to measure the distances but,rather, it is only necessary to mate the snaps on the straps 58 and 60with the mating portions on the mold halves 32 and 34. This prevents anoperator from forming an assembly with gaps that are too large.

Referring now to FIG. 14, there is illustrated an alternate embodimentof limiting the gap dimensions on interconnected mold segments. Alongitudinal flat member 70 is pivoted about a point 72 on the side ofthe mold 32. A sliding pin 74 is disposed on the end of the mold 34opposite the gap 44 from the mold half 32. The longitudinal member 70has a slot 76 formed therein that is dimensioned to fit over the slidingpin 74. At one extreme, the gap 44 is maximum and at the other extreme,the ends just abut. Therefore, the longitudinal member 70 maximizes thegap 44, allows the gap to narrow during curing and also prevents theends from abutting and pushing upward.

Referring now to FIGS. 15 and 16, there is illustrated an alternatemethod for ensuring that the gap 44 is formed. A spacing member 78 isdisposed in the gap 44 during the formation thereof. Rather thanutilizing the solid nylon strap 26 for securing the assembly, two thinnylon or Chlorobutyl straps 80 and 84 are disposed along thecircumferential edges of the mold halves 32 and 34. This secures themold halves to the built-up tire carcass 10 while the spacing member 78prevents the gap 44 from being reduced in width. After the assembly isformed, the spacing member 78 is removed and the tire processed asdescribed above.

Referring now to FIG. 17, there is illustrated an interlocking mechanismfor preventing lateral movement of the ends 16 and 18 of the mold 14.The interlocking mechanism consists of male plugs 86 attached to the end18 and aligned tangentially with the mold 14 and female receptacles 88in the end 16. The male plugs 86 are mated with the female receptacles88 such that closure of the gap 22 results in insertion of the maleplugs 86 into the female receptacles 88. In this manner, lateraldisplacement of the mold about the gap 22 is prevented.

In processing the tire from the initial casing to the final assemblythat is placed in the curing oven, the following process steps areutilized.

1. The tire casing has the outer surface thereof buffed and cementapplied thereto.

2. The cemented casing is placed on a tread builder with a stitcher arm.

3. A predetermined die size of uncured rubber is placed around the tirethat is disposed on the tread builder.

4. One of the mold sections for a two section mold is placed on top ofthe built up casing and the stitcher arm lowered to secure this moldagainst the casing.

5. The second half of the two piece mold is placed against the tire andeach of the gaps spliced with a layer of nylon tape unless one gap hasalready been spliced, in which case only the remaining gap need bespliced.

6. (optional) A length of nylon tape has one end thereof stapled to themold and then wrapped 360° about the mold to overlap with the other endof the tape and then the free end of the tape is stapled to the mold.The nylon tape is wet before placing about the tire. This tape holds thetwo mold sections securely against the built tire.

7. If necessary, a segment is disposed within the gap such that the endsare between 1/8th to 3/8th of an inch for a passenger tire or 1/4 to 1/2inch for a truck tire.

8. Each gap is covered with a cap.

9. A second layer of tape is applied and stapled around the cap tosecure the cap against the mold. The tape is prewet before disposal onthe mold.

10. The tape is allowed to dry for a short amount of time, resulting ina six to eight percent reduction in circumference. Steps 9 and 10 andoptional step 6 can be eliminated by using an elastic band fabricatedfrom Chlorobutyl.

11. The envelope is applied and then a rim is inserted into the tire andthe curing process is proceeded with.

In fabricating a recapped tire, any of the mold configurations describedabove can be utilized. The following are examples of such use.

Example 1

A single mold section having only one gap was utilized to recap a tirehaving a size 10.00-20 (bias). A tire carcass was built up to acircumference of 126.0625 inches. The mold was fabricated on a moldmatrix that had a circumference of 128.5 inches with a mold ribcircumferenc®measurement of 125.0 inches. The mold was applied to thebuiltup tire and stitched until the gap between the mold ends equalled0.5 inch. The tire was wrapped with wet nylon tape and covered with anenvelope. A rim was then applied to the tire and the tire was cured. Thecure time was three hours and forty five minutes at a temperature of260° F. The pressure inside of the tire carcass was 140 psi and thepressure external the tire was 70 psi. The resulting space between thebottom of the tread and the tire carcass, termed the "undertread",measured between 5/32-6/32 inches with the tread less than 1/8th of aninch off center. The adhesion of the cured tread pattern to the tirecarcass was 105 pounds per inch (ppi).

EXAMPLE 2

A two part equal length mold was formed and a tire recapped having atire size of 205/70R14 (radial). The built-up tire circumferencemeasured 79.875 inches with a mold rib circumference of 79.0 inches. Themold was stitched onto the built-up tire to yield a gap of 0.4375inches. The tire was covered by a butyl stretch band and a cap placedover each gap area. The tire was covered with an envelope for aspirationtherein and then placed on a rim and cured. The cure time was two hoursand fifteen minutes at a temperature of 300° F. The pressure withnn thetire was 105 psi and the pressure external to the tire was 70 psi. Thetire exhibited excellent definition of tread design with tread design1/8th inch off center.

In summary, there has been provided a recapping process for recappingbuilt-up tires with a segmented flexible mold. The segmented flexiblemold is placed around a built-up tire and the ribs forming the negativecontour of the tread pattern are then set into the uncured rubber on thebuilt-up tire. The mold is then secured against the built-up tire suchthat the ends of the molds segments have a gap formed therebetween. Thisassembly is placed into a curing envelope and then into a curing chamberfor curing thereof.

Although the preferred embodiment has been described in detail, itshould be understood that various changes, substitutions, andalterations can be made therein without departing from the spirit andscope of the invention as defined by the appended claims.

What is claimed is:
 1. Apparatus for recapping tires utilizing uncuredrubber and a prepared tire carcass, comprising:an arcuate segmentedelastomeric mold having a negative contour of a desired tread patternformed on one side thereof comprised of ribs operable to extenddownwardly into a layer of uncured rubber built-up around the tirecarcass, said segmented mold having a predefined length and at least twofree ends that are operable to abut and form a band when said ribs arefully imbedded in said layer of uncured rubber; means for securing saidsegmented mold around a circumferential surface of said built-up tirecarcass with a gap between said free ends and said ribs partiallyimbedded into said uncured rubber; and means for applying an externalforce radially inwardly to said segmented mold so that said ribs areforced into said uncured rubber during curing until said free ends ofsaid mold abut.
 2. The apparatus of claim 1 wherein said mold isfabricated from a chlorobutyl compound.
 3. The apparatus of claim 1wherein said segmented mold comprises;a first mold segment for disposalaround about one half of said built-up tire carcass; and a second moldsegment for disposal around about the other half of said built-up tirecarcass, said first and second mold segments dimensioned such that gapsbetween the free ends of said segments are formed having dimensionswithin a predetermined range of values.
 4. The apparatus of claim 1 andfurther comprising a sizing segment for disposal between the free endsof said segmented mold to reduce the gap therebetween and to account forvariations in sizes of said built-up tire carcass, said sizing segmenthaving the negative contour of the tread formed on an undersurfacethereof.
 5. The apparatus of claim 1 and further comprising a toroidalshaped flexible envelope for being fitted about said prepared tirecarcass and mold segment, said envelope directing radial forces inwardlyabout the surface of said mold section.
 6. The apparatus of claim 1wherein said means for applying an external force comprises an elasticband for disposal circumferentially about said mounted mold segments. 7.The apparatus of claim 1 and further comprising a semi-resilient cap fordisposal over the gap between the free ends of said mold segment forsecuring said free ends and preventing radial displacement outwardly. 8.The apparatus of claim 1 and further comprising means for preventingrelative lateral displacement of the free ends of said mold segments. 9.Apparatus for recapping tires utilizing uncured rubber and a preparedtire carcass, comprising:a first arcuate rubber mold segment having anegative contour of a desired tread pattern formed on an interiorsurface thereof, the negative contour formed of ribs extending radiallyinwardly; a second arcuate rubber mold segment substantially identicalto said first mold segment, said first and second mold segments beingadapted to enclose the prepared tire carcass and impress said negativecontour in a layer of uncured rubber which is built-up on the preparedtire carcass; said first and second segments each having a definedlength with a first and a second end; means for securing said first andsecond mold segments with gaps between adjacent said ends onto said tirecarcass such that a portion of said ribs is embedded into said layer ofuncured rubber; and means for forcing said first and second moldsegments radially inwardly to fully imbed said ribs and to abut saidends.
 10. The apparatus of claim 9 and further comprising a sizingsegment for disposal between said first and second mold segments toreduce the gap therebetween, said sizing segment utilized to accommodatevariances in a given tire size.
 11. The apparatus of claim 9 and furthercomprising first and second semi-resilient caps for disposal over thegaps between the ends of said first and second mold segments and meansfor securing said caps against said mold segments, said caps preventingradially outward displacement of the ends of said mold segments.
 12. Theapparatus of claim 9 wherein said force applying means comprises;anelastic strap disposed circumferentially about said mold segments; and aflexible envelope having a toroidal shape for disposal around said moldsegments and tightly conforming to the surface thereof to directpressure radially inward.
 13. The apparatus of claim 9 and furthercomprising means for preventing lateral displacement of the free ends ofsaid first and second mold segments relative to each other.
 14. Theapparatus of claim 1 wherein said means for applying an external forcecomprises means for applying an external force around a portion of thecircumferential surface of said mold so that said ribs are imbedded intosaid uncured rubber with a nonuniform depth.
 15. The apparatus of claim14 wherein said means for applying an external force comprises a rollerbed adapted for applying said nonuniform force around the circumferenceof said mold.
 16. The apparatus of claim 15 wherein said roller bedincludes rollers each arcuate shaped to receive therein said mold. 17.The apparatus of claim 9 further including spacer means for defining apredetermined distance between the free ends of said mold segments, andfor removing said spacer means prior to said curing.
 18. The apparatusof claim 17 wherein said spacer means comprises a block having apredetermined width, said block having no ribs.